Generate cryptographically strong passwords, memorable passphrases, or PINs with live entropy and crack-time estimates.
Three modes: random password (8 to 128 chars with character-class controls), passphrase (3 to 10 words from a curated 250-word list with separators), and PIN (4 to 12 digits). Strength meter shows entropy in bits and estimated crack time at 10 billion guesses per second.
Disclaimer: Never reuse passwords across sites. Always enable two-factor authentication where available. Store passwords in a vetted password manager.
Calculator information
📋 How to use this calculator
- Choose mode: Random Password, Passphrase, or PIN.
- For random password, set length 8-128 characters and tick the allowed character sets: uppercase, lowercase, digits, symbols.
- Enable the 'avoid ambiguous characters' option (0, O, 1, l, I) if the password will be typed manually.
- For passphrase, pick 3-10 words from the curated wordlist and a separator (space, hyphen, dot).
- For PIN, set length 4-12 digits and the 'avoid sequential patterns' option (1234, 1111).
- Check the entropy bits indicator and crack-time estimate; aim for at least 80 bits for important accounts per NIST SP 800-63B recommendations.
- Tips: never screenshot a password; use a password manager (Bitwarden, 1Password) to store it.
🧮 Entropy Bits and Crack Time
H = L * log2(N) ; crack_time_seconds = 2^H / (2 * G)
- H = total entropy (bits)
- L = password length (characters or words)
- N = charset size (94 for all printable ASCII, 7776 for the Diceware wordlist)
- G = attacker guesses per second (assumed 10^10 = 10 billion/sec for offline GPU)
- Factor of 2 in denominator: on average a password is found after half the space is searched
NIST SP 800-63B recommends a minimum of 8 characters for user-chosen passwords and 6 for machine-generated, with no forced composition rules. A 4-5 word Diceware passphrase is already strong (>50 bits).
💡 Worked example: Compare strength of a 12-character password vs a 4-word passphrase
Given:- Password 1: 12 characters, charset 94 (full ASCII)
- Password 2: 4-word passphrase from a 7776-word list
- Attacker rate: 10^10 guesses/sec
Steps:- Password 1: H = 12 * log2(94) = 12 * 6.55 = 78.6 bits.
- Crack time 1: 2^78.6 / (2 * 10^10) = 4.8 * 10^23 / 2 * 10^10 = 2.4 * 10^13 sec = 760,000 years.
- Password 2: H = 4 * log2(7776) = 4 * 12.92 = 51.7 bits.
- Crack time 2: 2^51.7 / (2 * 10^10) = 3.7 * 10^15 / 2 * 10^10 = 1.8 * 10^5 sec = approximately 50 hours.
- For 5 words: H = 64.6 bits, crack time rises to about 73 years.
Result: A 12-character random password is strong (760,000 years); a 4-word passphrase is only ~50 hours, so 5-6 words are needed for equivalence.
❓ Frequently asked questions
Is a longer password better than a complex one?
For brute-force attackers, entropy bits is what matters, and entropy grows linearly with length but only logarithmically with charset size. Adding one character with a 94-character charset adds 6.55 bits, while adding symbols to an 8-character password adds only about 4 bits. NIST SP 800-63B recommends prioritizing length over forced complexity.
Are password managers secure?
End-to-end encrypted password managers like Bitwarden, 1Password, or KeePass are far safer than memorizing passwords or storing them in notes. The master password is the only one you have to remember and should have high entropy (>80 bits). Independent audits are available for Bitwarden (open source) and 1Password.
What entropy is needed for a banking account?
US regulators (FFIEC, OCC, CFPB) do not specify exact entropy figures, but FFIEC guidance requires multi-factor authentication for high-risk online transactions. Best practice: a password of 12+ characters with entropy >=70 bits, plus 2FA via OTP or a hardware key (FIDO2/WebAuthn). Never reuse the same password across multiple banks.
Are EFF Diceware passphrases safe?
Yes, the EFF Large wordlist (7776 words) provides 12.92 bits per word when selected with physical dice or a CSPRNG. A 6-word passphrase produces 77.5 bits, exceeding the NIST minimum recommendation. The wordlist has been filtered to avoid biased, homophonic, or short-and-easily-mistyped words.
Does this calculator save generated passwords?
No. The entire process runs in the browser via the Web Crypto API; there are no server requests and no localStorage entries for passwords. You can verify this by opening DevTools and watching the Network tab while pressing Generate. Close the tab after moving the password into your password manager.
📚 Sources & references
Last updated: May 11, 2026